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			<h1>common_schema</h1> <strong>2.2</strong> documentation
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				<h2><a href="query_script_if_else.html">query_script_if_else</a></h2>	

<p>
QueryScript Flow Control: <strong>if-else</strong> statement
</p>

<h3>SYNOPSIS</h3>
<p>
<blockquote><pre>if (expression)
  statement;
[else
  statement;]
</pre></blockquote>
</p>

<h3>DESCRIPTION</h3>
<p> 
<i>if-else</i> is a flow control branching structure. It makes for a condition test based on
a given <a href="query_script_expressions.html">expression</a>. 
</p>
<p>
When the <i>expression</i> holds true, the statement (or block of statements) following the <i>if</i> statement are executed.
The <i>else</i> clause is optional, and it's statement(s) are executed when the <i>expression</i> does not hold true.
</p>
<p>
There is no built-in <i>elseif</i> clause. However, a chained <i>if-else if-else</i> statement is valid.
</p>
<p>
Empty statements are not allowed in QueryScript. 
However, empty blocks are, and a <i>if</i> or <i>else</i> clause may use an empty block statement, 
or by the do-nothing <a href="query_script_pass.html">pass</a> statement.
</p>


<h3>EXAMPLES</h3>
<p>
Simple <i>if-else</i> condition:
<blockquote><pre>
set @x := 17;
if (@x mod 2 = 0)
  SELECT 'even' AS answer;
else
  SELECT 'odd' AS answer;
</pre></blockquote>
</p>

<p>
<strong>DELETE</strong> statement as <i>expression</i>:
<blockquote><pre>
set @country := 'USA';
if (DELETE FROM world.Country WHERE Code = @country)
{
  -- We don't have foreign keys on these tables; do a manual drill down:
  DELETE FROM world.City WHERE CountryCode = @country;
  DELETE FROM world.CountryLanguage WHERE CountryCode = @country;
}
</pre></blockquote>
</p>


<p>
Using <i>if</i> to <a href="query_script_break.html">break</a> out of a <a href="query_script_while.html">while</a> loop: 
<blockquote><pre>
CREATE TEMPORARY TABLE test.numbers (n INT UNSIGNED NOT NULL PRIMARY KEY);
INSERT INTO test.numbers (n) VALUES (17);

set @n := 0;
while (@n < 20)
{
  if (INSERT IGNORE INTO test.numbers (n) VALUES (@n))
  {
  }
  else
  {
    break;
  }
  set @n := @n + 1;
}
SELECT @n AS inserted_up_to_this_value;

+---------------------------+
| inserted_up_to_this_value |
+---------------------------+
|                        17 |
+---------------------------+
</pre></blockquote>
</p>

<h3>SEE ALSO</h3>
<a href="query_script_while.html">while</a>,
<a href="query_script_expressions.html">expressions</a>

<h3>AUTHOR</h3>
Shlomi Noach
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